JP4161014B2 - Purification method for contaminated geology with organochlorine compounds - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a geological purification method, and more particularly to a contaminated geological purification method by an organic chlorine compound. In this specification, “geology” refers to all of the solid phase, liquid phase, and gas phase of the ground and underground, and means soil, formation, permeable layer, ground water, underground cavity, underground air, and the like.
[0002]
[Prior art and problems]
Organochlorine compounds, especially trichlorethylene and tetrachloroethylene, are low-boiling chlorine solvents, and are widely used in machine cleaning, dry cleaning factories, plating factories, semiconductor factories, etc. due to their excellent degreasing properties. Accumulation causes liver damage and central nervous system damage, and even a very small amount has been shown to be carcinogenic. It is a substance with a concentration of mg / l or less and 0.01 mg / l or less.
[0003]
Even if it is obligated to submit a manufacturing report under the Chemical Substances Control Regulation Law and it is specified as a water quality inspection item for groundwater such as well water, the above-mentioned organochlorine compounds continue to be used. The contaminated areas are still expanding, and therefore, there is a strong demand for purification treatment, but the actual purification measures are as follows.
[0004]
In other words, as a measure for the purification of geology contaminated with organochlorine compounds,
(1) Containment treatment methods such as embedding in concrete tanks and impervious sheets,
(2) Aeration treatment method and
(3) Use of methane-utilizing bacteria. Regarding contaminated soil and contaminated strata, there are a soil gas suction method and an underground air suction method.
[0005]
Of these measures, measure (1) is currently the most widely used, but this measure is symptomatic and cannot escape the possibility of leakage after a drought. Measure (2) uses the property that organochlorine compounds are easy to vaporize, but it requires a large-scale facility (aeration plant) to vaporize and detoxify, and it is still an environmental standard value. In practice, it takes a very long time, for example, several years in order to reduce the concentration to the following level. Countermeasure (3) is a methane-utilizing bacterium, that is, a methane-producing bacterium that decomposes methane into carbon dioxide and water through methanol, formaldehyde, and formic acid under aerobic conditions. It produces methane monooxygenase, which utilizes the fact that this enzyme also acts on organochlorine compounds and eventually decomposes into carbon dioxide, water and chloride ions. Although it has been proved effective in academic and laboratory settings, methane is required as an inducing substrate to activate the above-mentioned enzymes. Therefore, methane gas is required when decomposing organochlorine compounds in geology. However, it is not always practical, and because methane gas is flammable, it is dangerous. So there.
[0006]
[Problem to be Solved by the Invention]
Accordingly, the problem to be solved by the present invention or the object of the present invention is a method for purifying contamination by organochlorine compounds, has no problems as in the prior art, is extremely easy to implement, and has various geological features. It is to provide a purification method that can be used as a target.
[0007]
The present inventors have the advantage that methane-assimilating bacteria bring about complete decomposition of organochlorine compounds to carbon dioxide gas, water, and chloride ions at a high rate. We intensively studied to develop a purification method for organic chlorine compound contamination.
[0008]
As a result, the methane-utilizing bacteria are universally present in various geological environments, and the dissolved water is not used as a gas. If it is used in the form, it is necessary to avoid dangers such as explosions, improve the permeability to the ground, and provide an aerobic environment so that the conditions for the growth of methane-utilizing bacteria can be maintained. It has been found that it is necessary to penetrate to the water permeable layer in order to penetrate quickly and widely. Therefore, as a result of searching for a construction method that satisfies these conditions and conducting experiments, the present invention has been completed.
[0009]
[Means for Solving the Problems]
According to the present invention, the problem that the conventional methane-utilizing bacteria utilization method has is that methane gas is not methane-dissolved water prepared as a gas or artificially adjusted in the contaminated geology due to organochlorine compounds, but methane gas. It is solved by the purification method of contaminated geology by organochlorine compounds that injects the generated lake water and natural methane dissolved water taken from the underground of the gas field , and the intended purpose is achieved.
[0010]
The purification method according to the present invention can be carried out by excavating and forming pits (holes) in the ground and simply pouring methane-dissolved natural water into the pits, and is therefore very simple. Although there is no particular limitation on the opening area of the pit, it is preferable that the excavation depth reaches the permeable layer. This is because if methane-dissolved natural water is sent directly to the permeable layer, it can penetrate rapidly and over a wide area, and an aerobic environment is created for methane-utilizing bacteria present in the permeable layer. Because it gives. The methane-dissolved water used in the purification method according to the present invention is not artificially prepared by dissolving methane gas in well water, tap water, river water or spring water, but lake water or gas generating methane gas. The groundwater in the rice field, that is, methane-dissolved natural water is used . This is because such methane-dissolved natural water is easy to obtain and advantageous in terms of cost, and still contains methane-utilizing bacteria appropriately in the natural environment . The methane concentration of methane-dissolved natural water is generally in the range of about 500 to about 30000 Nmol / l.
[0011]
Of course, according to the present invention, it is also possible to purify the contaminated geology by introducing the geology contaminated with the organochlorine compound into methane-dissolved natural water containing methane-utilizing bacteria.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An example of the implementation of the purification method according to the present invention will be described with reference to the drawings. As shown in Fig. 1, the ground 10 is first excavated to form pits 12 for water injection and several observation wells 14. The drilling depth of pit 12 is set to reach the permeable layer 16, but if impossible, several wells are drilled from the bottom of the pit to reach the deep permeable layer. On the other hand, the drilling depth of the observation well 14 is set below the permeable layer 16 so that the concentration of organochlorine compounds at various depths can be measured.
[0013]
Next, methane-dissolved water was poured into pit 12, and after a predetermined time, taking into account the diffusion of methane-dissolved water 18 in the pit, water was collected using the observation well as a sample, and organic chlorine in the sample water was collected. The concentration of the compound is measured.
[0014]
【Example】
Next, the present invention will be described in more detail and specifically by examples.
Example First, multiple test wells were excavated in the planned cleanup area contaminated with organochlorine compounds, sampled to obtain sample water, and the PID gas chromatographic method was used to determine the status of contamination. As a result of detailed investigation, it was found that the organochlorine compound contaminating the groundwater in this area was trichlorethylene, the concentration was 0.20-0.05 mg / l, and the contaminated ground was a permeable layer.
[0015]
Next, a pit was formed by excavating the ground. The pit was 1.5m wide, 10m long and 3.5m deep, with the bottom reaching directly to the permeable layer where contamination was detected. The observation wells are the above test wells, and several wells separated by several meters each were used.
[0016]
After preparing the above preparations in advance, the groundwater existing in the gas field was taken, transported to the above purification countermeasure implementation area by a tank car, and poured into the above pit. The above groundwater is methane-dissolved natural water, the average methane concentration is about 30000 Nmol / l, the test period is 5 days, and the daily water injection to the pit is set to 5 tons.
[0017]
The trichlorethylene concentration was measured immediately before the start of the test, that is, immediately before the first injection of methane-dissolved groundwater into the pit, which was 0.20-0.05 mg / l as described above, but on the second day after the injection of methane-dissolved groundwater. The concentration dropped drastically and decreased to a concentration that could not be detected by detector tube measurement in any observation well, and this state was the same until the end of the test period. The detection limit concentration by this detector tube measurement is 0.1 ppm, which means that this detection limit concentration is 0.01 mg / l or less when converted to water pollution concentration. The standard value of 0.03 mg / l or less is completely cleared.
[0018]
【The invention's effect】
The purification method according to the present invention for geology contaminated with organochlorine compounds is basically very easy and simple to implement because methane-dissolved natural water is simply poured into a pit excavated in the ground. By setting the pit excavation depth to reach the permeable layer, it is possible to activate the methane-utilizing bacteria by providing an aerobic environment, and methane-dissolved natural water penetrates rapidly and over a wide area. Purification efficiency is improved. In particular, the use of natural methane-dissolved water taken from the lake water and gas field area where methane gas is generated is advantageous in terms of cost, and methane-utilizing bacteria are appropriately selected in the natural environment. Since it contains, a new methane-utilizing bacterium will be sent to the contaminated soil, thus improving the purification efficiency. Furthermore, since the present invention uses methane-utilizing bacteria present in natural methane-dissolved water , the methane-utilizing bacteria are activated and present in high density in the natural environment, and the conventional artificial The time required for purification treatment is drastically reduced when compared with methane-dissolved water by aeration treatment or the like adjusted to . In addition, the water, sediment, soil, etc. contaminated with the organic chlorine compound can be carried into the distribution area of the methane-dissolved natural water and treated with the methane-dissolved natural water for purification.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic view showing a procedure for carrying out a purification method according to the present invention.
[Explanation of symbols]
10: Ground
12: Pit
14: Observation well
16: Permeable layer (contaminated by organochlorine compound)
18: Methane-dissolved water (injected into pit 12)

Claims (4)

Purification of contaminated geology by organochlorine compounds, which is characterized by taking and injecting methane-dissolved natural water existing in lakes and gas fields where methane gas is generated into contaminated geology by organochlorine compounds Construction method. The method for purifying contaminated geology with an organic chlorine compound according to claim 1, wherein pits are excavated and formed on the ground, and methane-dissolved natural water is poured into the pits.   The method for purifying contaminated geology with organochlorine compounds according to claim 2, wherein the digging depth of the pit is set so as to reach the permeable layer. A method for purifying contaminated geology with organochlorine compounds, characterized in that the geology contaminated with organochlorine compounds is introduced into lake water producing methane gas or methane-dissolved natural water in gas fields .

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